We converted this document with your script without any problems. So the problem must be in your computer configuration.

First, try to convert your document with Batch Processing Application. If it can be converted with it, it means that there is something wrong with your script or options saved previously. If so, try to delete Print2Flash options stored on your computer. To accomplish this, delete the following registry key: HKEY_CURRENT_USER\Software\Print2Flash\Print2Flash3.

Can you convert documents successfully when SkipEmptySheets is false? What are you trying to accomplish with SkipEmptySheets property? The fact is this property is not documented and it is better not to use it.
Also, if you invoke document conversions from inside an Office plug-in and have access to Excel's Workbook object, it is better to convert using printing jobs rather than ConvertFile method.